All were from Iran's northern province of Mazandaran, Hossein Ali Rezayi, a Guards spokesman in the region, told the ISNA and Fars news agencies.
The casualties happened in Khan Tuman village some 10 kilometres southwest of the battleground city of Aleppo, according to a Guards statement, the official IRNA news agency reported.
Pro-regime troops had driven jihadists out of Khan Tuman in December, but fighting between regime forces and Al-Qaeda- affiliated jihadists and their allies killed more than 70 people south of Aleppo, a monitor said yesterday.
Around 30 pro-regime troops were killed in the battle, said the Britain-based Observatory which relies on a network of sources in Syria.
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Russia said yesterday that a temporary truce in Aleppo had been extended for 72 hours "in order to prevent the situation from worsening".
More than 300 civilians were killed in two weeks of fighting in the divided city before the truce took hold on Thursday, in regime air strikes on its opposition-held east and rebel shelling of the regime-controlled west.
Dozens of Iranian "advisers" have been killed in Syria since late 2015, including Revolutionary Guards commanders.